1. Technical Field
The present invention relates generally to communication networks and in particular to a method and system for enhancing a wireless communication network. Still more particularly, the present invention relates to a method and system for address resolution in an asymmetrical wireless communication network.
2. Description of the Related Art
The development of computerized information resources such as the xe2x80x9cInternetxe2x80x9d and the proliferation of xe2x80x9cWebxe2x80x9d browsers, allow users of data-processing systems to link with other servers and networks, and thus retrieve vast amounts of electronic information previously unavailable in an electronic medium. In electronic communications, a set of computer networks which are possibly dissimilar from one another are joined together by xe2x80x9cgatewaysxe2x80x9d that handle data transfer and the conversion of messages from the sending network to the protocols utilized by the receiving network, with packets if necessary. A gateway is a device utilized to connect dissimilar networks (i.e., networks utilizing different communication protocols) so that electronic information can be passed from one network to the other. Gateways transfer electronic information via wired connections converting such information to a form compatible the protocols utilized by the second network for transport and delivery.
The term xe2x80x9cInternetxe2x80x9d is an abbreviation for xe2x80x9cinter-network,xe2x80x9d and refers commonly to the collection of networks and gateways that utilize the xe2x80x9cTransport Control Protocol/Internet Protocol,xe2x80x9d (TCP/IP) suite of protocols, which are well-known in the art of computer networking.
An internetwork is a collection of individual Local Area Networks (LAN) and network links joined by routers. Each individual LAN or network link constitutes a subnetwork. For data to flow from a computer application, through the computer to an external interface, over a LAN, and out through a router to an internetwork, there must be addresses which identify all of the various interfaces utilized along the way. Routers read the IP address to determine which physical port the data unit should be transmitted through.
IP addresses and port numbers combined create a unique socket address, maintained and monitored by the operating system. The socket concept allows multiple users (identified by the IP addresses) to,address the same application (identified by the port address). IP addresses are utilized at the network layer to route data units through the internet. The IP address identifies a machine""s connection to the IP network not the physical address of a particular machine. Routers at the end of the delivery path must be responsible for changing the IP address into a machine address which can be utilized by the LAN protocol to deliver the data.
Internet Protocol (IP) is designed in general for application on symmetrical networks, where the properties of the outgoing and the incoming transmission links are identical. An important aspect involved in IP communication connection is the process of address resolution, implemented with the well known Address Resolution Protocol (ARP) when an unknown device is to be contacted. ARP resolves the Media Access Control (MAC) address currently associated with an IP address. The MAC address is the physical device address given by an authorized vendor, while the IP address classes are assigned statically or dynamically by a network.
In terrestrial networks with symmetric characteristics, address resolution is implemented as follows:
1. The requesting host broadcasts an ARP message with the source IP, MAC address, destination IP address and seeks the destination MAC address for IP visibility for subsequent Unicast communication; and
2. The destination host whose IP address matches the address in Step 1, responds to the requesting host with its MAC address filled in the appropriate field of the ARP message. Other hosts on the networks who receive the broadcast message in Step 1, and whose IP address does not match the destination IP address in step 1 will ignore the message.
In wireless networks (as in Satellite Systems) where the forward and the return transmission links utilize different underlying technologies (ex: Medium Frequency-Time Division Multiple Access (MF-TDMA) in return and Digital Video Broadcast (DVB) in forward), suitable modification to the address resolution procedures are required.
A technique for address resolution in a satellite system based on DVB in the forward link and a terrestrial telephone link in the return link (as in Hughes DirecPC) has been described in a technical report (ISR T.R. 96-20, Effective Extensions of Internet in Hybrid Satellite-Terrestrial Networks, Center for Satellite and Hybrid Communication Network). However, address resolution for a wireless system with asymmetrical communication links is not currently available. It would therefore be desirable and advantageous to have a method and system for address resolution in asymmetrical wireless communication networks.
It is one object of the present invention to provide an improved method and system for communication networks.
It is another object of the present invention to provide an improved method and system for enhancing a wireless communication network.
It is yet another object of the present invention to provide an improved method and system for address resolution in an asymmetrical wireless communication network.
The above features are achieved as follows. A method is disclosed for address resolution in a wireless system, with an originating interface terminal and a destination interface terminal. An Address Resolution Protocol (ARP) packet of a source is modified when transmitted from a source to a destination and when returned from the destination to the source. In an illustrative embodiment, the interface terminals are Satellite Interface Terminals (SIT) and the modification involves substituting the originating SIT address for that of the source in the ARP request packet and substituting the destination SIT address for that of the destination in the ARP reply packet, respectively.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.